Recirculating combustion apparatus



Aug. 28, 1962 B. R. WALSH RECIRCULATING COMBUSTION APPARATUS 2 Sheets-Sheet 1 Filed Aug. 5, 1958 INVENTOR. $9065 4?. 1444156 MvH' ATTORNEY Aug. 28, 1962 B. R. WALSH RECIRCULATING COMBUSTION APPARATUS 2 Sheets-Sheet 2 Filed Aug. 5, 1958 I A flm INVENTOR. 54 4/65 A. 1454156 ATTORNEY 3,5l,226 Patented Aug. 28, 1962 3,051,226 RECIRCULATING COMBUSTION APPARATUS Bruce R. Walsh, Pittsburgh, Pa., assignor to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware Filed Aug. 5, 1958, Ser. No. 753,254 10 Claims. (Cl. 158-1) This invention relates to fuel burning apparatus and more particularly to an improved combustion chamber for burning fuels with air.

For the generation of heat energy in fuel burning apparatus such as furnaces and boilers, a combustible mixture of air and a liquid or gaseous fuel are usually discharged directly into a combustion chamber wherein combustion of the fuel takes place. It is, of course, desirable to obtain substantially complete combustion of the fuel within the combustion chamber and it is to this end the present invention is directed.

The present invention provides a combustion chamber which is so constructed that the products of combustion are recirculated to the combustion zone in a manner to achieve greatly improved combustion and heating efficiency.

In accordance with the invention, there is provided a combustion chamber comprising an outer shell and an inner shell disposed within and spaced from the outer shell to define a passage between said shells for the recirculation of the products of combustion. The passage between the shells is closed at the top and suitable openings are provided in the inner shell to permit the hot gases produced upon combustion of the fuel to circulate through the combustion gas passage and to re-enter the combustion zone at a point near the fuel injector nozzle.

The invention will be further described with reference to the drawings wherein:

FIGURE 1 is a vertical sectional view of a complete furnace employing the combustion chamber of this invention.

FIGURE 2 is a perspective view of the combustion chamber of the invention.

FIGURE 3 is a plan view of the combustion chamber of the invention.

FIGURE 4 is a cross-sectional view taken through FIGURE 3 along the plane of the line IV-IV.

FIGURE 5 is a view similar to FIGURE 4 but illustrates a modified form of the combustion chamber of the invention.

FIGURE 6 is a front sectional view of the combustion chamber of the invention.

FIGURE 7 is a plan view of a further embodiment of the invention wherein the fire pot of a furnace is employed as one component of a combustion chamber constructed in accordance with the invention.

With reference to the drawings, the combustion chamber of the invention is illustrated in connection with a hotair type of furnace but it is to be distinctly understood that it is not limited to such use. The combustion chamber of the invention can be utilized in furnaces of the hot-air or hot-water types commonly employed in homes for heating and also in other fuel burning apparatus such as for example, gas turbine and jet engines to improve the combustion efiiciency thereof.

Referring to FIGURE 1, the numeral 11 designates a furnace of the hot-air type in which a combustion chamber constructed in accordance with the invention is employed. The upper part 12 represents, more or less, diagrammatically the heating chamber of the furnace. A fire pot 13 which'forms the lower section of the furnace is lined by refractory wall 14 and shaped to fit the contour of the furnace in which it is placed. The configuration of the fire pot will vary with the furnace and the fire pot may be, for example, circular, rectangular, square or hexagonal in shape. Port r15 is provided in the furnace for receiving the burner 16. The burner 16 can be any of the burners commonly used in the art for supplying a combustible mixture of a liquid or gaseous fuel and air to the combustion chamber. One such burner is the guntype burner which is utilized to supply a mixture of liquid fuel and air to the combustion chamber. A smoke pipe or flue stack is indicated at 17. A combustion chamber in accordance with the invention is located within the fire pot l3 and is designated generally by the numeral 18.

Referring more particularly to FIGURES 2, 3 and 4 of the drawings, the combustion chamber 18 of the invention comprises an outer shell adapted to fit within the fire pot of the furnace and an inner shell disposed therein defining a combustion zone. The outer shell generally indicated at 19 will be of suitable dimensions and shaped to fit within the fire pot of the furnace. The outer shell 19 open at its top, comprises substantially upright sheet metal side Walls 29 and 21, back wall 22, front wall 23, and bottom wall 24. Port 25 is provided in the front wall 23 for receiving the burner 16.

Disposed within outer shell 19 and spaced therefrom is an inner shell designated generally at 26 which defines a zone wherein combustion of the fuel takes place. Inner shell 26 open at its top, comprises substantially upright sheet metal side walls 27 and 28, back wall 29, front wall 30, and bottom wall 31. Secured to and depending from the bottom wall 31 are a plurality of legs 32 by means of which inner shell 26 is supported on the bottom wall 24- of outer shell 19 in spaced relationship therewith. The horizontal dimensions of inner shell 26 are such that the upright walls thereof are spaced from the adjacent walls of the outer shell 19 and cooperate therewith to provide a horizontal passage through which the products of combustion are recirculated to the combustion zone.

If desired, the inner shell can be constructed without the bottom wall as shown in FIGURE 5, in which case, the upright side, front and back walls of the inner shell bear upon the bottom wall 24 of the outer shell 19. It is preferred, however, to have the inner shell provided with a bottom wall and spaced from the bottom wall of the outer shell as this construction provides an additional open passage underneath the inner shell for the recircu1ation of the hot combustion gases.

The front wall 30 of the inner shell 26 is provided with port 33 which registers with port 25 in the outer shell and through which the air-fuel mixture enters the combustion zone. The burner 16, while projecting within the outer shell is positioned such that its discharge end terminates a short distance in front of port 33 so as to be capable of delivering a mixture of fuel and air to the interior of the inner shell without interfering with the flow of the combustion products. A plurality of openings are provided in the remaining Walls of the inner shell 26 to permit the products of combustion to exit from the combustion zone and to pass into the combustion gas passage between the inner and outer shells. Thus, side walls 27 and 28 of inner shell 26 are provided with a plurality of vertically elongated slot-like openings as indicated at 34, 35 and 36. Attached adjacent the vertical slot-like openings on the side walls and projecting inwardly within the inner shell 26 are louver members 37,

- 38 and 39. The louver members assist in directing the hot combustion gases through the slot-like openings into the space between the inner and outer shells. In a pre ferred optional construction, additional exits for the products of combustion are provided in the back and bottom walls of the inner shell. Thus, relatively large opening 40 is provided in back wall 29 of the inner shell opposite' port 33. Similarly, the bottom Wall 31 of the inner shell 26 can be provided with an opening as indicated at 41.

Extending horizontally and joining the top portions of the upright walls of the inner and outer shells is top 42. Top member 42 extends continuously along the marginal edges of the top portions of the upright walls of the inner and outer shells and is attached thereto by suitable means to form an air tight seal. Top member 42 thus cooperates with the upright walls of the inner and outer shell to form a closed or roofed passage which extends entirely around the inner shell. As shown in FIGURE 6, deflectors 43 and 44 are provided on the exterior surface of front wall 30 of inner shell 26 to direct the flow of hot combustion gases toward port 33 through which the combustion gases pass into the combustion zone.

For convenience in installation, both the inner and outer shell members can be made in sections so that the combustion chamber may be assembled in existing heating units after fabrication thereof. Thus, the inner and outer shells of the combustion chamber may comprise upper and lower matching sections or front and rear matching sections of a size to readily pass through the openings-normally provided in the front of the heating unit. Upon installing the combustion chamber the matching sections are brought together to complement one another and to form the combustion chamber in accordance with the invention.

'In operation of a fuel burning apparatus equipped with a combustion chamber constructed in accordance with the invention, burner 16 delivers a mixture of fuel and air into the inner shell 26 wherein combustion of the fuel occurs. As the flame progresses rearwardly within the inner shell, the hot products of combustion pass through the relatively large opening 40 provided in the back Wall 29 by the inner shell into the space defined by the walls of the inner and outer shells and the top member 42. The portion of the combustion products which impinge upon the back Wall of the inner shell and reflect therefrom, pass out through the openings 34, 35, 36 and 41 provided in the side and bottom walls respectively. The inwardly projecting louver members 37, 38 and 39 serve to direct the combustion products through the openings 34, 35 and 36 provided in the side walls of the inner shell. The combustion gases upon entering the space between the inner and outer shells are constrained to flow horizontally toward the front of the combustion chamber and eventually re-enter the combustion zone through port 33 provided in the front wall 30 of the inner shell 26. In this manner, the products of combustion are again subjected to combustion, thus providing a form of twostage combustion and assuring substantially complete fuel com-bustion. Inaddition, the hot combustion gases reentering the combustion zone at a point near the fuel injector nozzle convey heat to the incoming fuel and air and prime the mixturefor combustion.

In FIGURE 7, a further modification of the invention is illustrated. In this embodiment of the invention the walls defining the fire pot of the furnace serve as the outer shell of the improved combustion chamber. Referring specifically to FIGURE 7, thefire pot of the furnace made of refractory ceramic material and of hexagonal shape is indicated at 45. Disposed within fire pot 45 and spaced therefrom is the inner shell 46. Inner shell 46 can be made of ceramic material also or can .be of sheet .metal construction. The front wall of the inner'shell 46 is provided with port 47 which is aligned with port 48 in the front Wall of fire pot 45. The opposed back wall of inner shell 47 is provided with a relatively large opening as indicated at 49 which communicates with the combustion gas passagebetween the inner shell 46 and the walls of the fire pot 45. Elongated slot-like openings are provided along the remaining sides of the inner shell as indicated at 50, 51 and 52. Inwardly projecting louver members 53, 54 and 55 are attached adjacent the openings 50 and 51 and 52 respectively, and serve to direct combustion gases through these openings into the combustion gas passage. The entire outer surface of the walls comprising the inner shell 46 are spaced from the corresponding wall portions of the fire pot with the exception of the top 56. Top 56 is attached along the upper ends of the upright walls of the inner shell 46 and extends horizontally therefrom to have its outer ends in engagement with the wall portions of fire pot 45. To prevent leakage of the hot combustion gases, top 56 is cemented or joined by other suitable means to the fire pot 45. Thus, top member 56 cooperates with the upright walls of the fire pot 45 and inner shell 46 to form a closed combustion gas passage.

It will be apparent to those skilled in the art that various modifications can be made in the combustion chamber of the invention. Thus, for example, the outer and inner shells comprising the combustion chamber of the invention can be made of ceramic material instead of sheet metal as previously indicated. Moreover, the number of openings provided within the walls of the inner shell can be varied as desired.

From the foregoing description, it is apparent that the invention provides a novel combustion chamber of simple construction which can be readily installed in furnaces to improve the combustion efllciency of the furnaces. In the aforedescribed combustion chamber the hot products of combustion are recirculated through the chamber and subjected to combustion a second time thereby assuring substantially complete combustion of the fuel. An additional advantage of the novel combustion chamber is that the hot products of combustion upon reentering the combustion zone at a point near the fuel injector nozzle, supply heat to the incoming fuel and air thus assisting in the combustion of the fuel. Furthermore, in the combustion chamber of the invention, the hot combustion gases are prevented from being immediately exhausted up the stack thus resulting in the furnace having lower stack temperatures.

Those modifications and variations which fall within the spirit of the invention and the scope of the appended claims are to be considered part of the invention.

I claim:

1. A fuel burning apparatus comprising an outer shell, an inner shell having generally uprightwall means disposed within said outer shell and spaced therefrom to define a passage extending around the outer periphery of said upright wall means, the inside of said inner shell being a combustion chamber and said passage around said upright wall means adapted to serve as a recirculation passage for combustion gases from said combustion chamber, means closing the upper and lower ends of said recirculation passage, first opening means in said upright wall means adapted for the horizontal admission of fuel to said combustion chamber, said first opening means establishing an inlet to said combustion chamber from said recirculation passage, second opening means in said upright wall means establishing an outlet from said combustion chamber to said recirculation passage, said recirculation passage providing a path for circulation of combustion gases from said second opening means to said first opening means, said inner shell having an open top establishing overhead exhaust removal means from said combustion chamber, the only access between said overhead exhaust removal means and said recirculation passage being through said combustion chamber.

2. Claim 1 wherein said second opening means is disposed in said combustion chmaber in a position generally opposite to said first opening means.

3. Claim 1 wherein a nozzle is disposed substantially horizontally at said first opening means adapted for spraying a liquid fuel substantially horizontally into said combustion chamber.

4. A fuel burning apparatus comprising an outer shell having generally upright walls and a bottom wall, an

inner shell having generally upright Wall means disposed within said outer shell and spaced therefrom to define a passage extending around the outer periphery of said upright wall means, the inside of said inner shell being a combustion chamber and said passage around said upright wall means adapted to serve as a recirculation passage for combustion gases from said combustion chamber, means closing the upper and lower ends of said recirculation passage, first opening means in said upright wall means adapted for the horizontal admission of fuel to said combustion chamber, said first opening means establishing an inlet to said combustion chamber from said recirculation passage, second opening means in said upright wall means establishing an outlet from said combustion chamber to said recirculation passage, said recirculation passage providing a path for circulation of combustion gases from said second opening means to said first opening means, said inner shell having an open top establishing overhead exhaust removal means from said combustion chamber, the only access between said overhead exhaust removal means and said recirculation passage being through said combustion chamber.

5. Claim 4 wherein said upright inner shell wall means are shorter than said outer shell upright walls.

6. Claim 4 wherein an opening exists in an upright wall of the outer shell in register with the first opening means in the upright Wall means of the inner shell.

7. A fuel burning apparatus comprising an outer shell having generally upright walls and a bottom wall, an inner shell having generally upright wall means and bottom wall means disposed within said outer shell and spaced therefrom to define a passage extending around the outer periphery of said upright wall means and said bottom Wall means, support means for supporting said inner shell, the inside of said inner shell being a combustion chamber and said passage around the outer periphery of said upright wall means and said bottom wall means adapted to serve as a recirculation passage for combustion gases from said combustion chamber, means closing the upper end of said recirculation passage, first opening means in said upright wall means adapted for the horizontal admission of fuel to said combustion chamher, said first opening means establishing an inlet to said combustion chamber from said recirculation passage, second opening means in said upright wall means establishing an outlet from said combustion chamber to said recirculation passage, said recirculation passage providing a path for circulation of combustion gases from said second opening means to said first opening means, said inner shell having an open top establishing overhead exhaust removal means from said combustion chamber, the only access between said overhead exhaust removal means and said recirculation passage being through said combustion chamber.

8. Claim 7 wherein an opening exists in said bottom wall means of the inner shell providing an additional outlet from said combustion chamber to said recirculation passage.

9. A fuel burning apparatus comprising an outer shell having generally upright Walls and a bottom wall, an inner shell having generally upright Wall means and bottom wall means disposed within said outer shell and spaced therefrom to define a passage extending around the outer periphery of said upright Wall means and said bottom Wall means, legs supporting the bottom wall means of said inner shell, the inside of said inner shell being a combustion chamber and the passage around the periphery of said upright wall means and said bottom wall means adapted to serve as a recirculation passage for combustion gases from said combustion chamber, horizontal closure means continuously extending between the upper portion of the upright wall means of said inner shell and the upright walls of said outer shell to enclose the top of said recirculation passage, first opening means in said upright wall means adapted for the horizontal admission of fuel to said combustion chamber, said first opening means establishing an inlet to said combustion chamber from said recirculation passage, second opening means in said upright wall means establishing an outlet from said combustion chamber to said recirculation passage, said recirculation passage providing a path for circulation of combustion gases from said second opening means to said first opening means, said inner shell having an open top establishing overhead exhaust removal means from said combustion chamber, the only access between said overhead exhaust removal means and said recirculation passage being through said combustion chamber.

10. A fuel burning apparatus comprising an outer shell, an inner shell having generally upright wall means disposed within said outer shell and spaced therefrom to define a passage extending around the outer periphery of said upright wall means, the inside of said inner shell being a combustion chamber and said passage around said upright wall means adapted to serve as a recirculation passage for combustion gases from said combustion chamber, means closing the upper and lower ends of said recirculation passage, first opening means in said upright wall means adapted for the horizontal admission of fuel to said combustion chamber, said first opening means establishing an inlet to said combustion chamber from said recirculation passage, second opening means in said upright wall means in a position in said combustion chamber opposite to said first opening means establishing an outlet from said combustion chamber to said recirculation passage, third opening means comprising a plurality of openings in said upright wall means intermediate said first and said second opening means, each of the openings of said third opening means having an inwardly projecting louver adjacent thereto directed toward said second opening means, said recirculation passage providing a path for circulation of combustion gases from said second opening means and said third opening means to said first opening means, said inner shell having an open top establishing overhead exhaust removal means from said combustion chamber, the only access between said overhead exhaust removal means and said recirculation passage being through said combustion chamber.

References Cited in the file of this patent UNITED STATES PATENTS 1,671,448 Plassmann May 29, 1928 1,901,922 Mekler Mar. 21, 1933 1,959,033 McGuiness May 15, 1934 2,247,977 Uschold et al. July 1, 1941 2,424,765 McCollum July 29, 1947 2,601,667 Permann June 24, 1952 2,648,599 Throckmorton et al. Aug. 11, 1953 2,701,608 Johnson Feb. 8, 1955 2,808,046 Jaye Oct. 1, 1957 2,857,961 Brown et al. Oct. 28, 1958 2,918,117 Griflin Dec. 22, 1959 

